THE ANATOMY. SPERMATHECAE 127 



coelomic. These two sets of organs of different origin, but of similar function, will 

 be discussed here separately. 



(i) Spermathecae derived from invaginations of epidermis. This is the prevalent 

 form of the organ. Spermathecae of this kind are spherical, oval, or more elongated 

 pouches, with or without diverticula, varying in number and position, opening on to 

 the exterior by a more or less pronounced duct and, except in rare cases, ending 

 blindly at the other extremity. Like other organs developed from the epidermis, 

 the spermathecae do not, for the most part, show any ciliation ; in rare cases, which, 

 however, may possibly be commoner than is thought, a ciliation does occur ; it has 

 been described, for example, in Tubifex; and I have described a ciliation of the 

 spermatheca of Acanthodrilus rosae (43). Cilia seem to be out of place in a sac 

 communicating with the exterior and serving for 

 the storage of sperm. 



MICHAELSEN described, some years since, the 

 remarkable fact that in Enchytraeus mobii the 

 spermathecae instead of ending blindly opened 

 into the gut ; he was able to trace the bundles of 

 spermatozoa from the spermathecae into the lumen 

 of the gut by staining methods ; he has since SPERMATHECA OF 



shown that many, indeed most, Enchytraeidae MESENCHYTRAEUS BEUMERI. 



show the same remarkable connexion between (After Michaeisen.) 



the interior of the spermathecae and the lumen The upper extremity j. cut off where the 

 of the gut ; I can entirely confirm this discovery spermatheca opens into the gut. The two di- 



verticula contain sperm. 



for several species belonging to the family Enchy- 

 traeidae ; sometimes the aperture is at the tip of the spermatheca, at other times on 

 the side. More recently I have pointed out that in the genus Sutroa there is the 

 same communication between the two organs ; and in all probability Rhynckelmis 

 will be proved to agree with Sutroa. On a later page I shall have to direct 

 attention to the fact that in Paradi-ilus, where the spermathecae are of the second 

 type of these organs, the same thing occurs ; it seems, therefore, to be of functional, 

 rather than morphological, importance. Possibly, as has been suggested by MICHAELSEN, 

 this device ensures the getting rid of superfluous spermatozoa, which might otherwise 

 decay and cause injury to the animal by so doing. On the other hand, a second 

 suggestion might be made, which I give for what it may be worth; WHITMAN has 

 recently made the very interesting discovery that impregnation among the 

 Hirudinea may take place through the epidermis ; the spermatozoa apparently, in 

 some cases, force their way through the body-wall and fertilize the ova lying within 



